A recent significant advancement in the field of generating low temperature refrigeration is the pulse tube system or cryocooler wherein pulse energy is converted to refrigeration using an oscillating gas. Such systems can generate refrigeration to very low levels sufficient, for example, to liquefy helium. One important application of the refrigeration generated by such cryocooler system is in magnetic resonance imaging systems.
One problem with conventional cryocooler systems is contamination of the pulsing gas by the pulse generating equipment. Moreover, a source of inefficiency is a mismatch between the most efficient operating frequency of the cryocooler system and the most efficient operating frequency of the pulse generating system.
Accordingly it is an object of this invention to provide an improved cryocooler or pulse tube system which has reduced contamination potential and more efficient operation.